```
The challenge offers this example of how to use reduce to _subtract_ all the values of an array:
var singleVal = array.reduce(function(previousVal, currentVal) {
return previousVal - currentVal;
}, 0);
```

My question is: why wouldn’t the same code work by replacing the - (minus) sign with + (plus) in order to *add* the values of an array?

Here’s the code I used –

```
singleVal = array.reduce(function(previousVal, currentVal){
return previousVal+currentVal;});
```

but I still don’t understand why the example code wouldn’t work for addition as well as for subtraction.

Thanks.